Klong Hoi Khong Site (Thailand) Net primary production of a humid savanna grassland was determined at the Klong Hoi Khong study site belonging to Prince of Songkla University in southern Thailand. Monthly dynamics of live biomass and dead matter, above and below ground, were monitored from 1984 to the present, together with monthly litter bag estimates of decomposition rates above and below ... ground. The method for calculating net primary production accounted for simultaneous growth and death, and carbon flows to all trophic levels. Work was carried out under the United Nations Environment Program (UNEP) Project on "Primary Productivity of Grass Ecosystems of the Tropics" and has continued under subsequent UNEP and Thai-Austrian research projects. The study site of several hectares is situated within a larger experimental field area (6.3 N 100.9 E), about 40 km south-west of Hat Yai. Ancient shifting cultivation in the region originally converted the tropical forest to a savanna-like tree-grass mosaic on poorer soils. The study site has supported a humid savanna for at least the last 50-100 years, and is typical of the semi-natural pastures in the Thai/Malaysian Peninsula which were until recently commonly maintained by burning. However, much of the region is now under pressure for conversion to arable crops or rubber plantations. Net primary productivity was determined, initially under the auspices of an international collaborative UNEP Project, since there was a lack of information on the productive capacity and carbon cycling of the region. Complete data are available 1984-1990, including accidental burning in 1986 and 1989.